The annual birth rate and death rate per $1000$ are $39.4$ and $19.4$ respectively. The number of years in which population will be doubled assuming that there is no immigration or emigration approximately.

$P 8,000/-$ at $10\%$ p.a. interest compounded half yearly will become at the end of one year

If $P 1,000$ be invested at interest rate of $5\%$ and the interest be added to the principal every $10$ years, then the number in years in which it will amount to $P 2,000$ is:

A person borrows $P 5,000$ for $2$ years at $4\%$ per annual simple interest. He immediately lends to another person at $6.25\%$ per annum for $2$ years find his gain in the transaction for year:

If an amount is kept at S. I. it earns an interest of $P 600$ in first two years but when kept at compound interest it earns an interest of $P 660$ for the same period, then the rate of interest and principal amount respectively are:

If $P 10,000$ is invested at $8\%$ p.a. compounded quarterly, then the value of the investment after $2$ years is. (Given $(1.02)^8 = 1.171659)$

A bank pays $10\%$ rate of interest compounded annually. A sum of $P 400$ is deposited in the bank. The amount at the end of $1$ year will be